1. Field of the Invention
This invention relates to an X-ray exposure system, and more particularly, to an X-ray lithography system in which X-rays from a synchrotron radiation source are irradiated through a beryllium window onto the masked semiconductor wafer.
2. Description of the Related Art
In a lithography system, a semiconductor wafer or chip coated with a resist is exposed to beam radiation. Recently, in such lithographic radiation, an X-ray beam taken from synchrotron radiation has been used, in which X-rays from a synchrotron radiation source are irradiated through a beryllium window onto a masked semiconductor wafer, as disclosed in J. Vac. Sci. Technol. B 1(4), Oct.-Dec. 1983, pages 1262-1266.
The beryllium window is installed between a vacuum chamber for transmitting the X-ray beam and an atmospheric exposure chamber for accommodating wafers, and therefore, is subjected to a pressure, as will be mentioned hereinafter in detail. The beryllium window must, therefore, have sufficient mechanical strength to withstand a pressure, but on the other hand, if the thickness of the beryllium window could be reduced, the intensity of the X-ray beam transmitted therethrough would be increased, as also mentioned hereinafter in detail. Therefore, it would be advantageous if the thickness of the beryllium window were reduced.